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    <script>
        /*
            js中所有的数值都是Number类型
            包括整数和浮点数
        */
        
        var a = 123;
        console.log(a);
        var b = "123";
        /* 
            可以使用一个运算符typeof
            来检查一个变量的类型
            语法：typeof 变量
         */

         console.log(typeof a);
         console.log(typeof b);

        //  js中数字的最大值是  Number.MAX_VALUE
        console.log(Number.MAX_VALUE);

        //Infinity 代表无穷
        a = Infinity;
        console.log(Infinity);
        console.log(typeof a);

        //NaN = not a number
        a = NaN;
        console.log(typeof a);

        //最小值 Number.MAX_VALUE
        console.log(Number.MIN_VALUE);
    </script>
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